Study on the Immobilization of Bacillus mycoides and Removal of Heavy Metals Using Chitosan–Cellulose Composite Membranes

To improve the performance of water purification, this study combined membrane technology with microbial immobilization techniques to develop a novel membrane carrier adsorption pathway suitable for microbial immobilization. During the experiment, a coagulation bath of anhydrous ethanol at different mass fractions was first used to exchange ionic solvents in the chitosan (CS) and cellulose (CEL) blend solution. A composite membrane was then prepared using phase-inversion technology. Bacillus mycoides bacteria were then adsorbed onto and immobilized on the composite membrane surface. The membrane structure was further optimized by adjusting the fabrication conditions to enhance immobilization efficiency. Under optimized conditions (coagulation bath concentration of 30 wt% AE, CS:CEL ratio of 3:5, and DMSO:EMIMAc ratio of 1:2), the bacterial immobilization efficiency reached approximately 65%. The immobilized composite membrane exhibited enhanced heavy metal removal performance, achieving approximately 85% removal for Cu2+, 50% for Mn2+, and 33% for Li+ under optimized adsorption conditions (pH 6, initial concentration 10 mg·L−1, contact time 6 h). Isotherm and kinetic analyses revealed that the adsorption follows the Freundlich model for Cu2+ and Mn2+ and the Langmuir model for Li+, with pseudo-second-order kinetics governing the overall process. Subsequently, the impact of external environmental variations on the heavy metal removal capacity of the immobilized composite membrane was investigated. This research has significant scientific and practical value in addressing current freshwater scarcity and advancing water resource recycling.